The present inventions relates to a press which operates continuously to produce boards and wherein the material to be pressed is fed into a press slot between two movable surfaces of which at least one is defined by an endless belt, preferably of steel, which at the press slot is supported by a supporting surface in such a manner that it cannot increase its distance from the opposed moving surface.
The press herein is a press by means of which boards, such as particle boards, plywood boards, fiber boards and the like, may be pressed and various kinds of boards may be laminated and provided with a surface layer. In all such cases the boards or the board blanks must be subjected to pressure. The boards or the board blanks may constitute an endless web or constitute pieces of finite length and fed into the press one after the other.
In order to obtain, for boards of the kind indicated, a more flexible and simpler method of manufacture and processing, proposals have been made to replace the conventional multiple opening presses by continuously operating presses. The invention relates to such a continuously operating press.
If the press belt slides against a supporting surface there will be friction between the surface of the press belt and the supporting surface and such friction will brake the movement of the belt and generate therein a significant tensile stress and hence considerably limit the compression pressure. To a certain extent successful efforts have been made to reduce such friction by pumping an oil or air film between the belt and the supporting surface, but this entails considerable sealing problems and allows of not interspaces between the boards or width variations. A technically better solution has been obtained by introducing a number of roller chains between the belt and the supporting surface, such chains, like roller bearings, reducing the friction between the belt and the supporting surface to a minimum. The disadvantage of the last-mentioned solution primarily is that the roller bearings or roller rods must be specially made and require extremely high precision leading to very high manufacturing costs. Also, the guiding of the press belt and the rollers or roller rods will require sensitive and costly extra equipment.